Row in boxing arena because of matches where severe blow is likely (7,7)
I believe the answer is:
roaring forties
'where severe blow is likely' is the definition.
(the roaring forties are strong winds)
'row in boxing arena because of matches' is the wordplay.
'row' becomes 'oar' (oar can mean to row with oars).
'in' indicates putting letters inside.
'boxing arena' becomes 'ring' (boxing ring).
'because of' becomes 'for' (I've seen this in other clues).
'matches' becomes 'ties' (tie can mean a sporting fixture).
'oar' inserted inside 'ring' is 'roaring'.
'roaring'+'for'+'ties'='ROARING FORTIES'
(Other definitions for roaring forties that I've seen before include "stormy waters" , "weathering storms here?" .)